Sulige gas field is the most abundant natural gas field in Ordos Basin, North China. Because of the effect of sedimentation and diagenesis, reservoir heterogeneity is strong and the distribution of favorable reservoirs is... [ view full abstract ]
Sulige gas field is the most abundant natural gas field in Ordos Basin, North China. Because of the effect of sedimentation and diagenesis, reservoir heterogeneity is strong and the distribution of favorable reservoirs is complex. This paper systematically researches the influencing factors of reservoir quality differences of tight gas of Member 8, Shihezi Formation, Upper Permian in southern sulige gas field. Firstly, based on cores, outcrops, well logging, seismic and dynamic data, tight gas reservoir is finely characterized by using analytic hierarchy process. Then, the effect of sedimentation and diagenesis on the form and evolution of the tight gas reservoir is analyzed quantitatively. Finally, taking account of sedimentation and diagenesis, based on optimization of evaluation parameter, three types of reservoir (I, II and III) were classified by gray intensity analysis method, and the reservoir I is the best. Result shows: (1) reservoir quality differences of tight gas is controlled by sedimentary facies belt which include high-energy channel, low-energy channel, mid-channel bar and overbank sand. High-energy channel and mid-channel bar with favorable properties are high-quality reservoirs(I，II), whose lithology is mainly medium-coarse sandstone. But low-energy channel and overbank with poor properties belong to reservoir III, whose lithology is mainly fine siltstone. (2) The diagenesis is strong in research area. And the differentiation diagenetic evolution is another important reason to the differences of reservoir quality. Coarse-grained rock has the strong compressive resistance so that the compaction of it is weak. And to some degree, it could inhibit cementation. on the other hand, the differences of rock composition could lead differences of diagenesis. Quartz secondary overgrowth could make physical properties get worse, but feldspar and debris are more prone to occur dissolved, which leads to the form of the intergranular dissolved pore and intragranular dissolved pore. And the establishment of reservoir evaluation standard by gray intensity analysis could effectively predict favorable reservoir distribution found by study.
Topics: Diagenesis , Topics: Deltaic depositional systems
